I was trying to get a matching pair of rotors together, the two I do have, the compression faces are different! They both have the TII stamped inside of them but the outer edges have a different beveled edge, my guess is one is a very early generation TII rotor, and the other is a couple of years down the track.

The question is, can I use these as a matching pair, they've both been lightened, and the entire rotating assembly will get balanced, or should I go with too matching ones?

 

My guess is one is a S4 and one is a S5...

 

Don't the series 5/6/7 rotors have the machined face, you can see & feel the lines left by the mill from when they are produced.

Neither of these have these lines, I've taken a photo of what I think is a S5/6 rotor, and some photo's of the two rotor's in question.

 

They're both pre-S5. S5+ have machined tubs.

 

as long as they have the same compression ratio then you should be ok... just make sure one isnt N/A and the other TII

 

Did you already have them lightened?

If not, weigh them. The weight of a S5 rotor is roughly 9.5 lbs (4310 grams), the S4 rotor is roughly 10 lbs (4535 g).

The s4 has "as casted" tubs (compression dishes), and the s5 has machined tubs.

These both look to be s4, but to be completely sure, weigh them on a digital scale (post office should have one)

 

they have been lightened, but will weigh them anyway and go from there.

 

Lightened s4 rotors will never go much below the weight of a stock s5 rotor.

 

Those are both s4 rotors. s5 rotors have perfectly spaced lines/grooves in the compression bathtub, s4 and earlier were cast.

If the "T" is stamped on the non-gear-side beside the bearing, then they are low compression turbo rotors.